The present invention relates to a functional control device of the type set forth in the preamble of patent claim 1.
U.S. Pat. No. 4,261,273 relates to a pneumatic speed control device, designed for a sewing machine. This control device is actuated by means of a pneumatic breaker, which successively closes a plurality of contacts concurrently with an air pressure increase before the breaker, without any spark formation at the contacts. This control device is integrated with the sewing machine and is designed to directly actuate a machine function, namely the motor speed, but merely in one direction, namely forwardly or with a speed increase. No flexibility or adjustment as to different machines or machine types can be achieved by means of this control device. It is difficult or quite impossible to perform a pressure sensitivity and zero adjustment in practice. To use a plurality of movable parts results of course in a substantial disturbance sensitivity as well as elevated production and assembly costs. The control device is not conducive to making it easier for handicaped persons, and large foot movements are required in order to perform substantial speed changes. The used sensor, which is an entirely mechanical construction, is utterly objectionable for this purpose. A direct control using a high voltage is also an inconvenience.
Also, U.S. Pat. No. 4,722,288 relates to an electric sewing machine having an integrated computer designed to program needle work designs. Also, in this case the control device is integrated and cannot be separated from the machine to be controlled. The foot pedal, described in this document, is used solely to initiate and stop respectively a programmed or preprogrammed work operation, and it is not, like the document discussed above, conducive to helping a handicaped person, and large control movements are necessary.
The purpose of the present invention is to avoid the above-mentioned drawbacks and suggest a functional control device, which can be easily and simply adapted and connected to different machines in general terms and to different motor control means in particular, and which also is conducive to assisting a handicaped person, is simple, can be quickly and inexpensively produced and assembled and takes ergonomic and production engineering requirements into consideration, e.g. so called standing sewing operations.
These objects are attained by designing a functional control device, of the type mentioned in the introduction, according to the present invention.